Change to html5 (#958)

* Change to html5

with Nu Html Checker

* Update scale-pages.html

* Update sign.html

* Update common.html

* Update common.html

* Update login.html

src/main/resources/static/js/multitool/PdfActionsManager.js

@@ -4,7 +4,7 @@ class PdfActionsManager {
 
   constructor(id) {
     this.pagesContainer = document.getElementById(id);
-    this.pageDirection = document.documentElement.getAttribute("lang-direction");
+    this.pageDirection = document.documentElement.getAttribute("dir");
 
     var styleElement = document.createElement("link");
     styleElement.rel = "stylesheet";